Truck frame for construction machine

ABSTRACT

Left and right front flanges are provided respectively in left and right front legs in a center frame. Left and right rear flanges are provided respectively in left and right rear legs in the center frame. Left and right front leg mounting members, and left and right rear leg mounting members, which protrude toward the center frame are provided respectively in left and right side frames. The respective front flanges are placed on the respective front leg mounting members, which are respectively fastened by bolts inserted therebetween in the upper-lower direction. The respective rear flanges are placed on the respective rear leg mounting members, which are respectively fastened by bolts inserted therebetween in the upper-lower direction.

TECHNICAL FIELD

The present invention relates to a truck frame for a constructionmachine that is equipped with a crawler belt, such as a hydraulicexcavator, a hydraulic crane or the like, for example.

BACKGROUND ART

In general, a hydraulic excavator as a representative example of aconstruction machine comprises an automotive lower traveling structureprovided with a crawler belt, an upper revolving structure that ismounted on the lower traveling structure to be able to revolve thereon,and a working mechanism that is mounted to the upper revolving structureto be able to tilt thereto. The hydraulic excavator travels on anirregular ground such as a working site or the like, and performs anexcavating operation of earth and sand or the like using the workingmechanism.

In this case, the lower traveling structure in the hydraulic excavatoris regularly configured of a truck frame that is provided with sideframes at both sides of a center frame in the left-right direction toextend in the front-rear direction, an idler wheel that is provided onone end side of the side frame in the front-rear direction, and a drivewheel that is provided on the other end side of the side frame in thefront-rear direction. A crawler belt is wound around between the idlerwheel and the drive wheel.

The center frame in the truck frame has front legs and rear legs thatextend in both sides in the left-right direction, and the left and rightside frames are positioned at both sides of the center frame in theleft-right direction to be formed extending in the front-rear direction,and are respectively mounted to tip ends of the front leg and the rearleg.

Here, some of large-sized hydraulic excavators among the hydraulicexcavators have an outer dimension exceeding a width dimension or aheight dimension within a range where the hydraulic excavator can travelon a road defined by regulations. Therefore, in a case of transportingthe hydraulic excavator to a working site, the hydraulic excavator isregularly divided into the lower traveling structure, the upperrevolving structure and the working mechanism, which are individuallytransported, and are assembled in the working site. Further, in anextremely large-sized hydraulic excavator used in an open-pit mining orthe like, only the lower traveling structure exceeds a dimension withina range where the hydraulic excavator can go through the road.Therefore, the lower traveling structure is divided into three piecesconfigured of the center frame, and left and right side frame assembliesin which the idler wheel, the drive wheel and the crawler belt areincorporated in each of the left and right side frames. Accordingly, thecenter frame and the left and right side frame assemblies that are thusconfigured of the three-divided pieces are individually loaded ondifferent vehicles to be transported to a working site, and after that,are assembled in the working site.

Therefore, the truck frame forming part of the lower traveling structureis configured such that the left and right side frames can be mounted toand removed from the front legs and the rear legs of the center frame.In this case, each of the front leg and the rear leg of the center framehas an end surface at the front end side that is formed in a hollow,square shape, and a front end side of each of the front leg and the rearleg is provided with a mounting flange having a protruding portionprotruding closer to an outside than the square end surface. On theother hand, each of the left and right side frames comprises an innersurface plate that is positioned in a side of the center frame and withwhich the mounting flange makes contact, an outer surface plate that isarranged to face the inner surface plate to be spaced therefrom, and anupper surface plate that connects an upper end of the inner surfaceplate and an upper end of the outer surface plate.

The inner surface plate of the side frame is provided with plural femalescrews in positions corresponding to the protruding portion of themounting flange of each of the front leg and the rear leg, and theprotruding portion of the mounting flange is provided with bolt throughholes in positions corresponding to the respective female screws. Thefront end side of each of the front leg and the rear leg is providedwith a bracket in which plural bolt through holes are formed, and theupper surface plate of the side frame is provided with plural femalescrews in positions corresponding to the respective bolt through holesof the bracket. In a case of mounting each side frame to the front legand the rear leg of the center frame, the bolt is inserted in each boltthrough hole in the mounting flange of each of the front leg and therear leg from the inside in the left-right direction, and a front endside of the bolt is screwed into the female screw of the inner surfaceplate in the side frame. Further, the bolt is inserted into each boltthrough hole of the bracket in each of the front leg and the rear legfrom above, and a front end side of the bolt is screwed into the femalescrew of the upper surface plate of the side frame (Patent Document 1).

PRIOR ART DOCUMENT Patent Document

Patent Document 1: Japanese Patent Laid-Open No. 2001-73409 A

SUMMARY OF THE INVENTION

Incidentally, rocks and the like roll over in a working site where ahydraulic excavator travels. Therefore, there are some cases when thehydraulic excavator goes through across the rock for avoidance attraveling, the rock collides with the truck frame. In this case, since ahead portion of the bolt fastening the side frame on each of the frontleg and the rear leg of the center frame protrudes inside of the sideframe, there is a possibility that, when the rock across which thehydraulic excavator has gone through collides with the bolt, the bolt isdamaged (broken, bent or the like). In a state where the bolt is thusbent, it requires labors and hours to perform a removal work of the sideframe.

On the other hand, the upper surface plate of the side frame is formedof a flat structure, which therefore is the structure where earth andsand tend to be easily accumulated. Accordingly, upon accumulation ofearth and sand thereon, the earth and sand interfere with upper rollersthat guide a crawler belt, possibly generating an operation failure orearly abrasion of the upper roller. Further, in a case where theaccumulated earth and sand are solidified by compression or freezing,there is a problem that a large deal of labors and hours is required toscrape the earth and sand off the upper surface plate of the side frame.

In view of the aforementioned problems in the conventional art, it is anobject of the present invention to provide a truck frame for aconstruction machine that can prevent damages of bolts for fasteningside frames to front legs and rear legs of a center frame.

(1) A truck frame for a construction machine according to the presentinvention comprises a center frame on a central part of which a supportcylindrical body is provided and that includes front legs and rear legsat both sides in the left-right direction; and left and right sideframes that are respectively positioned at both sides of the centerframe in the left-right direction to be formed extending in thefront-rear direction and are respectively mounted to tip ends of thefront legs and the rear legs, wherein the center frame comprises: anupper plate on an upper surface side of which the support cylindricalbody is provided and at both sides in the left-right direction of whichupper front leg portions and upper rear leg portions are provided; alower plate that is arranged to face the upper plate in the upper-lowerdirection and at both sides in the left-right direction of which lowerfront leg portions and lower rear leg portions are provided; a frontplate that closes a front side position between the upper plate and thelower plate; a rear plate that closes a rear side position between theupper plate and the lower plate; and left and right side plates thatrespectively close left and right side positions between the upper plateand the lower plate, wherein each of the left and right side framescomprises: an inner surface plate positioned in a side of the centerframe; an outer surface plate arranged to face the inner surface plate,to be spaced therefrom; and an upper surface plate that connects anupper end of the inner surface plate and an upper end of the outersurface plate.

In order to solve the aforementioned problems, the constitution adoptedby the present invention is characterized in that: front flangesprotruding in the front-rear direction from the lower front leg portionsare provided in the lower front leg portions forming part of the centerframe and rear flanges protruding in the front-rear direction from thelower rear leg portions are provided in the lower rear leg portions,front bolt through holes that penetrate in the upper-lower direction areprovided in the front flange and rear bolt through holes that penetratein the upper-lower direction are provided in the rear flange, a frontleg mounting member that protrudes toward the center frame to be mountedto the front flange and a rear leg mounting member that protrudes towardthe center frame to be mounted to the rear flange are respectivelyprovided in the inner surface plate forming each of the left and rightside frames, and female bolt holes are provided in the front legmounting member and the rear leg mounting member respectively inpositions corresponding to the bolt through holes, wherein in a statewhere the front and rear flanges of the center frame are placedrespectively on the front and rear leg mounting members of the left andright side frames, the bolts are inserted in the bolt through holes andthe female bolt holes, thereby mounting the left and right side framesto the center frame.

With this arrangement, since the flanges provided in the front leg andthe rear leg of the center frame and the front and rear leg mountingmembers provided on the inner surface plate of the side frame aremounted by the bolts inserted in the upper-lower direction, the headportion of the bolt can be positioned on an upper surface of eachflange. Therefore, it is possible to restrict the rock to make contactwith the head portion of the bolt at the traveling of the constructionmachine to prevent damages, the bending or the like of the bolt. As aresult, for example, the bolt can be easily pulled out at the time ofremoving the side frame from the front leg and the rear leg of thecenter frame to efficiently perform a removing work of the side frame.

Further, since the front and rear leg mounting members are provided onlyon the inner surface plates of the left and right side frames, it ispossible to mount the leg mounting members at the possible upward side.Therefore, in a state where the front leg and the rear leg of the centerframe are respectively mounted on the front and rear leg mountingmembers, a height dimension from the ground surface to the lower surfaceof the center frame can be set to be high. Therefore, it is possible toprevent the rock from making contact with the lower surface of thecenter frame at the traveling of the construction machine to enhancetraveling safety of the construction machine.

(2) According to the present invention, each of the front and rear legmounting members provided in each of the left and right side framescomprises: mounting plates that protrudes from the inner surface plateof each of the left and right side frames toward the center frame and onwhich each of the front and rear flanges is placed; and a reinforcingplate that is fixed to a lower surface of the mounting plate and theinner surface plate of each of the left and right side frames forreinforcing the mounting plate.

With this arrangement, strength of each leg mounting member can beenhanced. Therefore, the center frame, and the left and right sideframes can be strongly mounted to enhance reliability of theconstruction machine.

(3) According to the present invention, each of the front and rear legmounting members comprises the mounting plate that is configured of aflat plate extending in the horizontal direction, and the reinforcingplate comprises a flat plate that is arranged in the upper-lowerdirection to be perpendicular to the lower surface of the mountingplate, wherein the mounting plate and the reinforcing plate areconnected to be formed in a T-letter shape.

With this arrangement, the flange can stably be placed on the mountingplate extending in the horizontal direction. Along with it, connectingstrength of the mounting plate and the reinforcing plate can be ensuredto improve support strength of each leg mounting member.

(4) According to the present invention, the front bolt through holesprovided in the respective front flanges of the left and right frontlegs in the center frame are arranged in the front and rear positions ofthe lower front leg portions respectively, the rear bolt through holesprovided in the respective rear flanges of the left and right rear legsin the center frame are arranged in the front and rear positions of thelower rear leg portions respectively, the female bolt holes provided inthe front leg mounting member of each of the left and right side framesare arranged in the front and rear positions of the front leg mountingmember respectively to oppose the front bolt through holes, and thefemale bolt holes provided in the rear leg mounting member of each ofthe left and right side frames are arranged in the front and rearpositions of the rear leg mounting member respectively to oppose therear bolt through holes.

With this arrangement, the front flange of each of the left and rightfront legs in the center frame can stably be mounted on the front legmounting member of each of the left and right side frames by the bolts,and the rear flange of each of the left and right rear legs in thecenter frame can stably be mounted on the rear leg mounting member ofeach of the left and right side frames by the bolts.

(5) According to the present invention, each of the left and right sideframes has one end side of the front-rear direction provided with anidler wheel and the other end side provided with a drive wheel, theupper surface plate of each of the left and right side frames isprovided with a plurality of upper roller devices positioned between theidler wheel and the drive wheel to be spaced from each other, and aninclined cover is provided between the respective upper roller devicesto be inclined to an oblique downward side from the inner surface platetoward the outer surface plate, which form part of each of the left andright side frames.

With this arrangement, earth and sand can be discharged along theinclined cover. Thereby, accumulation of earth and sand on the uppersurface plate of each of the left and right side frames can berestricted to control interference of the earth and sand with the upperroller device. As a result, the upper roller device can smoothly operateover a long period of time. In addition, since the accumulation of theearth and sand on the upper surface plate of the side frame can berestricted, it is not necessary to wash out earth and sand by use of agreat deal of hours and labors, thus making it possible to enhanceworkability of the washing work.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view showing an extremely large-sized hydraulicexcavator provided with a truck frame according to a first embodiment ofthe present invention.

FIG. 2 is a front view shown by enlarging a lower traveling structure inFIG. 1.

FIG. 3 is a partial cutaway plan view showing a state where side framesand the like are mounted to a center frame.

FIG. 4 is an exploded perspective view showing the center frame.

FIG. 5 is an exploded perspective view showing the center frame, andleft and right side frames.

FIG. 6 is a partially enlarged cross section showing a state where theleft side frame is mounted to a left rear leg as viewed in a directionof arrows VI-VI in FIG. 3.

FIG. 7 is a cross section showing a state where the left rear leg andthe left side frame are exploded at the same position with that of FIG.6.

FIG. 8 is a partially enlarged cross section showing a state where theleft side frame is mounted to the left rear leg as viewed in a directionof arrows VIII-VIII in FIG. 3.

FIG. 9 is a plan view showing a truck frame according to a secondembodiment of the present invention as similar to FIG. 3.

FIG. 10 is an exploded perspective view showing a center frame, left andright side frames, inclined covers and the like in FIG. 9.

FIG. 11 is a partially enlarged cross section showing the center frame,the side frame, the inclined cover and the like as viewed in a directionof arrows XI-XI in FIG. 9.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a truck frame for a construction machine according toembodiments in the present invention will be in detail explained withreference to the accompanying drawings, by taking a case of beingapplied to an extremely large-sized hydraulic excavator as an examplethereof. It should be noted that a front side and a rear side of a lowertraveling structure change with a revolving position of an upperrevolving structure, but in the embodiments, an explanation will be madeby defining a side where an idler wheel is provided, as a front side ofthe truck frame, and a side where a drive wheel is provided, as a rearside of the truck frame.

FIG. 1 to FIG. 8 show a first embodiment of a truck frame for aconstruction machine according to the present invention.

In FIG. 1, designated at 1 is a hydraulic excavator as a representativeexample of a construction machine. The hydraulic excavator 1 isconfigured as an extremely large-sized hydraulic excavator. Thehydraulic excavator 1 schematically comprises a crawler type lowertraveling structure 2 that is capable of self-traveling, an upperrevolving structure 4 that is mounted through a revolving device 3 onthe lower traveling structure 2 to be capable of revolving thereon, anda working mechanism 5 that is tiltably provided in the front side of theupper revolving structure 4 thereto for performing an excavatingoperation of earth and sand, or the like.

The crawler type lower traveling structure 2 is provided for travelingon an irregular ground and the like where rocks roll over and a lot ofconcave and convex portions exist. As shown in FIG. 2 and FIG. 3, thelower traveling structure 2 schematically comprises a truck frame 11,which will be described later, an idler wheel 6 that is provided in afront end side of each of left and right frames 25 and 29, which will bedescribed later, a drive wheel 7 that is provided in a rear end sidethereof, a plurality of upper roller devices 8 and lower roller devices9 that are provided in each of the left and right side frames 25 and 29,and a crawler belt 10 that is provided to be wound across between theidler wheel 6 and the drive wheel 7 and is guided by the upper rollerdevices 8 and the lower roller devices 9.

Next, the configuration of the truck frame 11 of the hydraulic excavator1 that forms a characteristic part of the present invention will beexplained with reference to FIG. 2 and FIG. 8.

Designated at 11 is the truck frame that forms a support structure ofthe lower traveling structure 2. The truck frame 11 comprises a centerframe 12, a left side frame 25, and a right side frame 29, which will bedescribed later.

Indicated at 12 is the center frame that forms a central part of thetruck frame 11. The center frame 12 comprises a center frame body 12Apositioned in the center, a left front leg 12B and a right front leg 12Cextending outside in the left-right direction at the front side of thecenter frame body 12A, and a left rear leg 12D and a right rear leg 12Eextending outside in the left-right direction at the rear side of thecenter frame body 12A to be formed in a substantially H-letter shape asa whole. As shown in FIG. 4, the center frame 12 is formed as a canningstructure by welding an upper plate 13, a lower plate 15, a front plate17, a rear plate 18, a left side plate 19, and a right side plate 20,which will be described later.

The upper plate 13 is provided to close an upper side of the centerframe 12, and is formed in a flat shape of a substantially H-letter typeas a whole by a steel plate or the like. An upper surface side of theupper plate 13 is provided with a support cylindrical body 14 in acylindrical shape. Specifically, the upper plate 13 comprises an uppercenter plate portion 13A in a substantially rectangular shape forming acentral part thereof, a left upper front leg portion 13B in asubstantially rectangular shape and a right upper front leg portion 13Cin a substantially rectangular shape each protruding from a frontportion side of the upper center plate portion 13A to both the sides inthe left-right direction, and a left upper rear leg portion 13D in asubstantially rectangular shape and a right upper rear leg portion 13Ein a substantially rectangular shape each protruding from a rear portionside of the upper center plate portion 13A to both the sides in theleft-right direction. Thereby, the upper plate 13 is formed as a platebody in a substantially H-letter shape as a whole. An upper surface sideof the upper center plate portion 13A is provided with the supportcylindrical body 14 formed of a thick cylindrical body. Here, since therevolving device 3 is provided on the support cylindrical body 14, thesupport cylindrical body 14 rotatably supports the upper revolvingstructure 4.

The lower plate 15 is arranged to face the upper plate 13 in theupper-lower direction, and is formed as a flat plate in a substantiallyH-letter shape as similar to the upper plate 13. An upper surface sideof the lower plate 15 is provided with a cylindrical middle plate 16thereon. Specifically, the lower plate 15 comprises a lower center plateportion 15A in a substantially rectangular shape forming a central partthereof, a left lower front leg portion 15B in a substantiallyrectangular shape and a right lower front leg portion 15C in asubstantially rectangular shape each protruding from a front portionside of the lower center plate portion 15A to both the sides in theleft-right direction, and a left lower rear leg portion 15D in asubstantially rectangular shape and a right lower rear leg portion 15Ein a substantially rectangular shape each protruding from a rear portionside of the lower center plate portion 15A to both the sides in theleft-right direction. Thereby, the lower plate 15 is formed as a platebody in an H-letter shape as substantially similar to the upper plate 13as a whole.

On the other hand, a large diameter hole 15F is formed in the centralpart of the lower center plate portion 15A. An upper surface side of thelower center plate portion 15A is provided with the cylindrical middleplate 16 in a cylindrical shape thereon that surrounds the largediameter hole 15F. The cylindrical middle plate 16 supports the supportcylindrical body 14 mounted on the upper plate 13 from under. Left andright front flanges 21A and 21B which will be described later arerespectively provided to be integral with a front side and a rear sideof each of the left and right lower front leg portions 15B and 15C. Leftand right rear flanges 22A and 22B are respectively provided to beintegral with a front side and a rear side of each of the left and rightlower rear leg portions 15D and 15E.

The front plate 17 connects the upper plate 13 and the lower plate 15 ina state of closing a front side position therebetween. As shown in FIG.4, the front plate 17 is formed of two sheets of plate bodies in arectangular shape extending in the left-right direction, and the frontplate 17 comprises a left front plate 17A and a right front plate 17B.In the left front plate 17A and the right front plate 17B, opposingsections of each other are welded to an outer peripheral surface 16A ofthe cylindrical middle plate 16, an upper end portion of each is weldedto the upper plate 13 and a lower end portion of each is welded to thelower plate 15. As a result, the front plate 17 is tightly fixed betweenthe upper plate 13 and the lower plate 15.

A rear plate 18 connects the upper plate 13 and the lower plate 15 in astate of closing a rear side position therebetween. As shown in FIG. 4,the rear plate 18 is formed of two sheets of plate bodies in arectangular shape extending in the left-right direction, and the rearplate 18 comprises a left rear plate 18A and a right rear plate 18B. Theleft rear plate 18A and the right rear plate 18B face with each other tohave the front plate 17 and the cylindrical middle plate 16therebetween, opposing sections of each other are welded to the outerperipheral surface 16A of the cylindrical middle plate 16, an upper endportion of each is welded to the upper plate 13 and a lower end portionof each is welded to the lower plate 15. As a result, the rear plate 18is tightly fixed between the upper plate 13 and the lower plate 15.

The left side plate 19 connects the upper plate 13 and the lower plate15 in a state of closing a left side position therebetween, and the leftside plate 19 is formed of four sheets of plate bodies in a rectangularshape. That is, the left side plate 19 comprises a left front side plate19A that is welded to the left upper front leg portion 13B of the upperplate 13 and the left lower front leg portion 15B of the lower plate 15,a left front middle side plate 19B that faces the left front plate 17Ain the front-rear direction and is welded to the left upper front legportion 13B, the left lower front leg portion 15B and the cylindricalmiddle plate 16, a left rear side plate 19C that is welded to the leftupper rear leg portion 13D of the upper plate 13 and the left lower rearleg portion 15D of the lower plate 15, and a left rear middle side plate19D that faces the left rear plate 18A in the front-rear direction andis welded to the left upper rear leg portion 13D, the left lower rearleg portion 15D and the cylindrical middle plate 16.

The right side plate 20 connects the upper plate 13 and the lower plate15 in a state of closing a right side position therebetween, and theright side plate 20 is formed of four sheets of plate bodies in arectangular shape. That is, the right side plate 20 comprises a rightfront side plate 20A that is welded to the right upper front leg portion13C of the upper plate 13 and the right lower front leg portion 15C ofthe lower plate 15, a right front middle side plate 20B that faces theright front plate 17B in the front-rear direction and is welded to theright upper front leg portion 13C, the right lower front leg portion 15Cand the cylindrical middle plate 16, a right rear side plate 20C that iswelded to the right upper rear leg portion 13E of the upper plate 13 andthe right lower rear leg portion 15E of the lower plate 15, and a rightrear middle side plate 20D that faces the right rear plate 18B in thefront-rear direction and is welded to the right upper rear leg portion13E, the right lower rear leg portion 15E and the cylindrical middleplate 16.

That is, the center frame 12 has four sides that are closed by the frontplate 17, the rear plate 18, the left side plate 19 and the right sideplate 20 around the cylindrical middle plate 16. As shown in FIG. 3 toFIG. 5, in a state where the center frame 12 is assembled, the leftfront flange 21A of the front flange 2 which will be described later isformed to protrude respectively closer to the front side than the leftfront plate 17A of the front plate 17 and closer to the rear side thanthe left front middle side plate 19B of the left side plate 19.Likewise, the right front flange 21B of the front flange 21 is formed toprotrude respectively closer to the front side than the right frontplate 17B of the front plate 17 and closer to the rear side than theright front middle side plate 20B of the right side plate 20. The leftrear flange 22A of the rear flange 22 is formed to protrude respectivelycloser to the rear side than the left rear plate 18A of the rear plate18 and closer to the front side than the left rear middle side plate 19Dof the left side plate 19. Likewise, the right rear flange 22B of therear flange 22 is formed to protrude respectively closer to the rearside than the right rear plate 18B of the rear plate 18 and closer tothe front side than the right rear middle side plate 20D of the rightside plate 20.

Indicated at 21A and 21B are the left front flange and the right frontflange respectively protruding in the front-rear direction from the leftand right lower front leg portions 15B and 15C of the lower plate 15(hereinafter, the left front flange 21A and the right front flange 21Bare collectively called the front flange 21). The front flange 21 isarranged at four locations that is a sum of two locations of the leftfront flanges 21A protruding respectively from the front side and therear side of the left lower front leg portion 15B, and two locations ofthe right front flanges 21B protruding respectively from the front sideand the rear side of the right lower front leg portion 15C. The leftfront flange 21A is mounted on a left front leg mounting member 33A ofthe left side frame 25 which will be described later, and the rightfront flange 21B is mounted on a right front leg mounting member 33B ofthe right side frame 29.

Indicated at 22A and 22B are the left rear flange and the right rearflange respectively protruding in the front-rear direction from the leftand right lower rear leg portions 15D and 15E of the lower plate 15(hereinafter, the left rear flange 22A and the right rear flange 22B arecollectively called the rear flange 22). The rear flange 22 is arrangedat four locations that is a sum of two locations of the left rearflanges 22A protruding respectively from the front side and the rearside of the left lower rear leg portion 15D, and two locations of theright rear flanges 22B protruding respectively from the front side andthe rear side of the right lower rear leg portion 15E. The left rearflange 22A is mounted on a left rear leg mounting member 36A of the leftside frame 25 which will be described later, and the right rear flange22B is mounted on a right rear leg mounting member 36B of the right sideframe 29.

Indicated at 23A and 23B are left and right front bolt through holesthat are respectively provided in the left and right front flanges 21Aand 21B of the lower plate 15 (hereinafter, the left front bolt throughhole 23A and the right front bolt through hole 23B are collectivelycalled the front bolt through hole 23). Here, the front bolt throughhole 23 is provided to penetrate through the front flange 21 in theupper-lower direction (thickness direction). That is, the left frontbolt through holes 23A are provided on four locations in the front-sideleft front flange 21A protruding in the front side from the left lowerfront leg portion 15B, and are also provided on four locations in therear-side left front flange 21A protruding in the rear side from theleft lower front leg portion 15B. On the other hand, the right frontbolt through holes 23B are provided on four locations in the front-sideright front flange 21B protruding in the front side from the right lowerfront leg portion 15C, and are also provided on four locations in therear-side right front flange 21B protruding in the rear side from theright lower front leg portion 15C.

Indicated at 24A and 24B are left and right rear bolt through holes thatare respectively provided in the left and right rear flanges 22A and 22Bof the lower plate 15 (hereinafter, the left rear bolt through hole 24Aand the right rear bolt through hole 24B are collectively called therear bolt through hole 24). Here, the rear bolt through hole 24 isprovided to penetrate through the rear flange 22 in the upper-lowerdirection (thickness direction). That is, the left rear bolt throughholes 24A are provided on four locations in the front-side left rearflange 22A protruding in the front side from the left lower rear legportion 15D, and are also provided on four locations in the rear-sideleft rear flange 22A protruding in the rear side from the left lowerrear leg portion 15D. On the other hand, the right rear bolt throughholes 24B are provided on four locations in the front-side right rearflange 22B protruding in the front side from the right lower rear legportion 15E, and are also provided on four locations in the rear-sideright rear flange 22B protruding in the rear side from the right lowerrear leg portion 15E.

Designated at 25 is the left side frame that is arranged in the leftside of the center frame 12. The left side frame 25 is formed to extendin the front-rear direction, and is mounted to a tip end of the leftfront leg 12B and a tip end of the left rear leg 12D. The left sideframe 25 schematically comprises a side frame body 26, an idler wheelbracket 27, and a drive wheel bracket 28, which will be described later.

The side frame body 26 forms part of a base of the left side frame 25.The side frame body 26 comprises an inner surface plate 26A positionedin a side of the center frame 12, an outer surface frame 26B arranged toface the inner surface plate 26A in a state of being spaced therefrom,and a flat upper surface plate 26C connecting an upper end of the innersurface plate 26A and an upper end of the outer surface plate 26B.Thereby, the side frame body 26 is formed in a reverse U-letter shape intransverse section, and lower sides of the respective surface plates 26Aand 26B are respectively provided with bottom plates 26D.

The upper surface plate 26C is provided with a plurality of (three)upper roller devices 8 thereon, which are positioned between the idlerwheel 6 and the drive wheel 7 to be spaced from each other in thefront-rear direction, for guiding the crawler belt 10. The upper rollerdevice 8 comprises a pair of left and right roller mounting portions 8Athat are arranged on the upper surface plate 26C as a flat surface, anda roller 8B that is rotatably mounted between the pair of the rollermounting portions 8A.

The idler wheel bracket 27 is provided in the front side in the sideframe body 26. As shown in FIG. 3, the idler wheel 6 is mounted througha yoke (not shown) and the like on the idler wheel bracket 27 to bemovable in the front-rear direction. On the other hand, the drive wheelbracket 28 is provided in the rear side in the side frame body 26. Thedrive wheel 7 for driving the crawler belt 10 is mounted on the drivewheel bracket 28.

Indicated at 29 is the right side frame that is arranged in the rightside of the center frame 12. The right side frame 29 is formed to extendin the front-rear direction, and is mounted to a tip end of the rightfront leg 12C and a tip end of the right rear leg 12E. The right sideframe 29 is formed to be symmetrical to the aforementioned left sideframe 25 in the left-right direction, and schematically comprises, assimilar to the left side frame 25, a side frame body 30, an idler wheelbracket 31, and a drive wheel bracket 32.

The side frame body 30 forms part of a base of the right side frame 29.The side frame body 30 comprises an inner surface plate 30A positionedin a side of the center frame 12, an outer surface plate 30B arranged toface the inner surface plate 30A in a state of being spaced therefrom,and a flat upper surface plate 30C connecting an upper end of the innersurface plate 30A and an upper end of the outer surface plate 30B.Thereby, the side frame body 30 is formed in a reverse U-letter shape intransverse section, and lower sides of the respective surface plates 30Aand 30B are respectively provided with bottom plates (not shown).

The upper surface plate 30C is provided with a plurality of (three)upper roller devices 8 thereon, which are positioned between the idlerwheel 6 and the drive wheel 7 to be spaced from each other in thefront-rear direction, for guiding the crawler belt 10. The upper rollerdevice 8 comprises a pair of left and right roller mounting portions 8Athat are arranged on the upper surface plate 30C as a flat surface, anda roller 8B that is rotatably mounted between the pair of the rollermounting portions 8A.

The idler wheel bracket 31 is provided in the front side in the sideframe body 30. As shown in FIG. 3, the idler wheel 6 is mounted througha yoke (not shown) and the like on the idler wheel bracket 31 to bemovable in the front-rear direction. On the other hand, the drive wheelbracket 32 is provided in the rear side in the side frame body 30. Thedrive wheel 7 for driving the crawler belt 10 is mounted on the drivewheel bracket 32.

Next, front and rear leg mounting members 33 and 36 that are provided ineach of the left and right side frames 25 and 29 will be explained.

Designated at 33A and 33B are left and right front leg mounting membersthat are provided in each of the inner surface plate 26A of the leftside frame 25 and the inner surface plate 30A of the right side frame 29(hereinafter, the left front leg mounting member 33A and the right frontleg mounting member 33B are collectively called a front leg mountingmember 33). Here, since the left front leg mounting member 33A which isprovided in the left side frame 25 and the right front leg mountingmember 33B which is provided in the right side frame 29 are formed ofthe same configuration, hereinafter the left front leg mounting member33A provided in the left side frame 25 will be explained.

The left front leg mounting member 33A is arranged in the front side(idler wheel bracket 27-side) of the inner surface plate 26A in the sideframe body 26 forming part of the left side frame 25, and protrudeshorizontally toward the center frame 12. The left front leg mountingmember 33A is configured by connecting (welding joint) a mounting plate34 and a reinforcing plate 35 in a T-letter shape.

That is, the mounting plate 34 is formed in a rectangular flat plateextending horizontally in the front-rear direction by using a steelplate or the like, and has a base end side that is welded to the innersurface plate 26A of the side frame body 26 and a front end side thatprotrudes toward the left front leg 12B of the center frame 12. Thereinforcing plate 35 is formed as a plate body in a substantiallytriangular shape by using a steel plate or the like, and is fixed to alower surface (not shown) of the mounting plate 34 and the inner surfaceplate 26A of the left side frame 25 in the upper-lower direction to beperpendicular to the lower surface (not shown) of the mounting plate 34for reinforcing the mounting plate 34. The left front flange 21Aprovided in the left lower front leg portion 15B of the lower plate 15that forms part of the center frame 12 is placed on the upper surfaceside of the mounting plate 34.

On the other hand, the right front leg mounting member 33B provided inthe inner surface plate 30A of the side frame body 30 that forms part ofthe right side frame 29 is also configured in the same way as the leftfront leg mounting member 33A described above, and the right frontflange 21B provided in the right lower front leg portion 15C of thelower plate 15 that forms part of the center frame 12 is placed on theupper surface side of the mounting plate 34.

Designated at 36A and 36B are left and right rear leg mounting membersthat are provided respectively in the inner surface plate 26A of theleft side frame 25 and the inner surface plate 30A of the right sideframe 29 (hereinafter, the left rear leg mounting member 36A and theright rear leg mounting member 36B are collectively called a rear legmounting member 36). Here, since the left rear leg mounting member 36Awhich is provided in the left side frame 25 and the right rear legmounting member 36B which is provided in the right side frame 29 areformed of the same configuration, hereinafter the left rear leg mountingmember 36A provided in the left side frame 25 will be explained.

The left rear leg mounting member 36A is arranged in the rear side(drive wheel bracket 28-side) in the inner surface plate 26A of the sideframe body 26 that forms part of the left side frame 25, and protrudeshorizontally toward the center frame 12. The left rear leg mountingmember 36A is configured by connecting (welding joint) a mounting plate37 and a reinforcing plate 38 in a T-letter shape.

That is, the mounting plate 37 is formed of a rectangular flat plateextending horizontally in the front-rear direction by using a steelplate or the like, and has a base end side that is welded to the innersurface plate 26A of the side frame body 26 and a front end side thatprotrudes toward the left rear leg 12D of the center frame 12. Thereinforcing plate 38 is formed as a plate body in a substantiallytriangular shape by using a steel plate or the like, and is fixed to alower surface 37A of the mounting plate 37 and the inner surface plate26A of the left side frame 25 in the upper-lower direction to beperpendicular to the lower surface 37A of the mounting plate 37 forreinforcing the mounting plate 37. The left rear flange 22A provided inthe left lower rear leg portion 15D of the lower plate 15 that formspart of the center frame 12 is placed on an upper surface side of themounting plate 37.

On the other hand, the right rear leg mounting member 36B provided inthe inner surface plate 30A of the side frame body 30 that forms part ofthe right side frame 29 is also configured in the same way as the leftrear leg mounting member 36A described above, and the right rear flange22B provided in the right lower rear leg portion 15E of the lower plate15 that forms part of the center frame 12 is placed on the upper surfaceside of the mounting plate 37.

Indicated at 39 are female bolt holes provided in each of the front legmounting member 33 and the rear leg mounting member 36. The female boltholes 39 are provided in a position corresponding to the front boltthrough hole 23 provided in the front flange 21 and in a positioncorresponding to the rear bolt through hole 24 provided in the rearflange 22.

In the first embodiment, the female bolt holes 39 are provided in theleft front leg mounting member 33A of the left side frame 25 in eightlocations that are a sum of four holes in each of the front position andthe rear position of the left front leg mounting member 33A of the leftside frame 25. Similarly, the female bolt holes 39 are provided in theright front leg mounting member 33B of the right side frame 29 in eightlocations that are a sum of four holes in each of the front position andthe rear position of the right front leg mounting member 33B of theright side frame 29.

The female bolt holes 39 are provided in the left rear leg mountingmember 36A of the left side frame 25 in eight locations that are a sumof four holes in each of the front position and the rear position of theleft rear leg mounting member 36A of the left side frame 25. Similarly,the female bolt holes 39 are provided in the right rear leg mountingmember 36B of the right side frame 29 in eight locations that are a sumof four holes in each of the front position and the rear position of theright rear leg mounting member 36B of the right side frame 29.Consequently, the female bolt holes 39 are provided at 32 locations intotal.

Indicated at 40 is a bolt on an outer periphery of a shaft portion ofwhich a male screw is provided, and the bolts 40 are providedrespectively between the front flange 21 (21A and 21B) and the front legmounting member 33 (33A and 33B) and between the rear flange 22 (22A and22B) and the rear leg mounting member 36 (36A and 36B) for connection(fixation) of both. The bolt 40 is inserted in the front bolt throughhole 23 or the rear bolt through hole 24 through a sleeve 40B from anupper side to a lower side of the front flange 21 or the rear flange 22,and is screwed into the female bolt hole 39 of the front leg mountingmember 33 or the rear leg mounting member 36. In this state, the sleeve40B is interposed between a head portion 40A of the bolt 40 and thefront flange 21 or the rear flange 22 in the upper-lower direction.

In case of mounting the left side frame 25 and the right side frame 29on the center frame 12, the front flanges 21A and 21B provided in thelower front leg portions 15B and 15C of the lower plate 15 forming partof the center frame 12 are placed on the left front leg mounting member33A provided on the inner surface plate 26A of the left side frame 25,and on the right front leg mounting member 33B provided on the innersurface plate 30A of the right side frame 29, respectively. The rearflanges 22A and 22B provided in the lower rear leg portions 15D and 15Eof the lower plate 15 forming part of the center frame 12 are placed onthe left rear leg mounting member 36A provided on the inner surfaceplate 26A of the left side frame 25, and on the right rear leg mountingmember 36B provided on the inner surface plate 30A of the right sideframe 29, respectively. In this state, the front bolt through holes 23Aand 23B and the rear bolt through holes 24A and 24B provided in thefront flanges 21A and 21B and the rear flanges 22A and 22B, and thefemale bolt holes 39 provided in the front leg mounting members 33A and33B and the rear leg mounting members 36A and 36B are positioned on thesame axis line to be screwed through the bolts 40. Therefore, the leftside frame 25 and the right side frame 29 can be mounted to the centerframe 12.

The hydraulic excavator 1 according to the first embodiment has theconfiguration as described above, and an explanation will be made of awork where the lower traveling structure 2 of the extremely large-sizedhydraulic excavator 1 is divided to be transported, and the lowertraveling structure 2 that has been divided will be assembled in aworking site.

In a case of transporting the large-sized hydraulic excavator 1 to aworking site, for example, the lower traveling structure 2 is dividedinto three pieces of the center frame 12, a left side frame assembly inwhich the idler wheel 6, the drive wheel 7, the crawler belt 10 and thelike are incorporated on the left side frame 25, and a right side frameassembly in which the idler wheel 6, the drive wheel 7, the crawler belt10 and the like are incorporated on the right side frame 29. The centerframe 12, the assembly of the left side frame 25, and the assembly ofthe right side frame 29 are individually loaded on different vehicles tobe transported to the working site.

In the working site, the assembly work of the center frame 12, the leftside frame 25 and the right side frame 29 will be performed.

In a case of mounting the left side frame 25 to the center frame 12, thecenter frame 12 is lifted up, the left front side plate 19A of the leftfront leg 12B and the left rear side plate 19C of the left rear leg 12Dare caused to make contact with the inner surface plate 26A of the leftside frame 25. In this state, the left front flange 21A provided in theleft lower front leg portion 15B of the lower plate 15 is placed on themounting plate 34 of the left front leg mounting member 33A provided inthe inner surface plate 26A of the left side frame 25. Along with it,the left rear flange 22A provided in the left lower rear leg portion 15Dof the lower plate 15 is placed on the mounting plate 37 of the leftrear leg mounting member 36A provided in the inner surface plate 26A ofthe left side frame 25. At this time, the left front bolt through hole23A of the left front flange 21A and the female bolt hole 39 of the leftfront leg mounting member 33A are positioned on the same axis line, andsimilarly the left rear bolt through hole 24A of the left rear flange22A and the female bolt hole 39 of the left rear leg mounting member 36Aare positioned on the same axis line.

Next, the bolt 40 is inserted in the left front bolt through hole 23Athrough the sleeve 40B from an upper side of the left front flange 21A,and the bolt 40 is screwed in the female bolt hole 39 of the left frontleg mounting member 33A. The bolt 40 is inserted in the left rear boltthrough hole 24A through the sleeve 40B from an upper side of the leftrear flange 22A, and the bolt 40 is screwed in the female bolt hole 39of the left rear leg mounting member 36A. Thereby, the left side frame25 is mounted to be integral with the left front leg 12B and the leftrear leg 12D of the center frame 12.

On the other hand, in a case of mounting the right side frame 29 on thecenter frame 12, the center frame 12 is lifted up, and the right frontside plate 20A of the right front leg 12C and the right rear side plate20C of the right rear leg 12E are caused to make contact with the innersurface plate 30A of the right side frame 29. In this state, the rightfront flange 21B provided in the right lower front leg portion 15C ofthe lower plate 15 is placed on the mounting plate 34 of the right frontleg mounting member 33B provided in the inner surface plate 30A of theright side frame 29. Along with it, the right rear flange 22B providedin the right lower rear leg portion 15E of the lower plate 15 is placedon the mounting plate 37 of the right rear leg mounting member 36Bprovided in the inner surface plate 30A of the right side frame 29. Atthis time, the right front bolt through hole 23B of the right frontflange 21B and the female bolt hole 39 of the right front leg mountingmember 33B are positioned on the same axis line, and similarly the rightrear bolt through hole 24B of the right rear flange 22B and the femalebolt hole 39 of the right rear leg mounting member 36B are positioned onthe same axis line.

Next, the bolt 40 is inserted in the right front bolt through hole 23Bthrough the sleeve 40B from an upper side of the right front flange 21B,and the bolt 40 is screwed in the female bolt hole 39 of the right frontleg mounting member 33B. The bolt 40 is inserted in the right rear boltthrough hole 24B through the sleeve 40B from an upper side of the rightrear flange 22B, and the bolt 40 is screwed in the female bolt hole 39of the right rear leg mounting member 36B. Thereby, the right side frame29 is mounted to be integral with the right front leg 12C and the rightrear leg 12E of the center frame 12.

When the left side frame 25 and the right side frame 29 are mounted tothe center frame 12 to assemble the lower traveling structure 2, theupper revolving structure 4 and the working mechanism 5 are in turnassembled on the upper side of the lower traveling structure 2, thusmaking it possible to assemble the hydraulic excavator 1.

At the traveling of the hydraulic excavator 1 assembled as describedabove, the drive wheel 7 is driven for rotation, which causes thecrawler belt 10 to circle around between the drive wheel 7 and the idlerwheel 6. Thereby, the hydraulic excavator 1 travels to an excavatingsite, and an excavating operation of earth and sand or the like can beperformed by tilting the working mechanism 5 in this excavating site.

Here, in working sites where the hydraulic excavator 1 travels, most ofthem are irregular grounds where obstacles of rocks and the like rollover. Therefore, there are some cases where the rock collides with thetruck frame 11 at the time of going through across the rock attraveling. In this case, as in the case of the conventional art, whenthe head portion of the bolt connecting between the center frame and theleft and right side frames protrudes in the inner side of each sideframe in the left-right direction, there is a possibility that the rockwhich the hydraulic excavator 1 has gone through collides with the headportion of the bolt to damage (break, bend or the like) the bolt.

On the other hand, according to the first embodiment, the left frontflange 21A provided in the left lower front leg portion 15B of the lowerplate 15 forming part of the center frame 12 is placed on the left frontleg mounting member 33A provided in the inner surface plate 26A of theleft side frame 25. Along with it, the left rear flange 22A provided inthe left lower rear leg portion 15D of the lower plate 15 is placed onthe left rear leg mounting member 36A provided in the inner surfaceplate 26A of the left side frame 25. In this state, the bolts 40 areinserted in the left front bolt through hole 23A and the left rear boltthrough hole 24A provided in the left front flange 21A and the left rearflange 22A from upward to downward. Next, the bolts 40 are screwed inthe female bolt holes 39 provided in the left front leg mounting member33A and the left rear leg mounting member 36A, and thereby the left sideframe 25 can be mounted to the center frame 12.

A case of mounting the right side frame 29 on the center frame 12 isalso similar to that of the left side frame 25. That is, the right frontflange 21B provided in the right lower front leg portion 15C of thelower plate 15 forming part of the center frame 12 is placed on theright front leg mounting member 33B provided in the inner surface plate30A of the right side frame 29. Along with it, the right rear flange 22Bprovided in the right lower rear leg portion 15E of the lower plate 15is placed on the right rear leg mounting member 36B provided in theinner surface plate 30A of the right side frame 29. In this state, thebolts 40 are inserted in the right front bolt through hole 23B and theright rear bolt through hole 24B provided in the right front flange 21Band the right rear flange 22B from upward to downward. Next, the bolts40 are screwed in the female bolt holes 39 provided in the right frontleg mounting member 33B and the right rear leg mounting member 36B, andthereby the right side frame 29 can be mounted to the center frame 12.

Accordingly, the head portions 40A of the bolts 40 for mounting the leftside frame 25 and the right side frame 29 to the center frame 12protrude from upper surfaces of the left and right front flanges 21A and21B and the left and right rear flanges 22A and 22B. In addition, asshown in FIG. 6, the lower ends of the bolts 40 can be accommodatedupward of lower surfaces 37A of the mounting plates 37 of the rear legmounting members 33 and 36 (not protrude from the lower surfaces 37A).Similarly, the lower ends of the bolts 40 can be accommodated upward oflower surfaces (not shown) of the mounting plates 34 of the front legmounting members 33 (not protrude from the lower surfaces 34). As aresult, it is possible to be difficult for the rock to make contact withthe head portion 40A of the bolt 40 at the traveling of the hydraulicexcavator 1 to prevent damages, bending or the like of the bolt 40.Thereby, for example, the bolt can easily be pulled out at the time ofremoving the left and right side frames 25 and 29 from the front legs12B and 12C and the rear legs 12D and 12E of the center frame 12, thusperforming a removal work of the left and right side frames 25 and 29efficiently.

On the other hand, since the front leg mounting member 33 and the rearleg mounting member 36 are respectively provided in each of the innersurface plates 26A and 30A of the respective side frames 25 and 29, eachof the upper surface plates 26C and 30C of the side frames 25 and 29 canbe configured as a flat surface. Therefore, even if earth and sandkicked up by the crawler belt 10 are accumulated on the upper surfaceplates 26C and 30C of the left and right side frames 25 and 29, anoperator can easily scrape the earth and sand at the time of performinga cleaning work of the hydraulic excavator 1.

According to the first embodiment, since the front leg mounting member33 (33A and 33B) and the rear leg mounting member 36 (36A and 36B) arerespectively provided only in the inner surface plate 26A of the leftside frame 25 and in the inner surface plate 30A of the right side frame29, the front leg mounting member 33 and the rear leg mounting member 36can be mounted as upward as possible. Therefore, in a case of mountingthe front legs 12B and 12C and the rear legs 12D and 12E of the centerframe 12 on the front and rear leg mounting members 33 and 36, a heightdimension A from the ground surface to the lower surface of the centerframe 12 can be set to be high (refer to FIG. 6). Thereby, it ispossible to reduce contact of rocks or the like with the lower surfaceof the center frame 12 at the traveling of the hydraulic excavator 1 toenhance traveling stability of the hydraulic excavator 1.

Next, FIG. 9 to FIG. 11 show a second embodiment of the presentinvention. The present embodiment is characterized in that an inclinedcover is provided for preventing earth and sand from being accumulatedon the upper surface of each of the left and right side frames. Itshould be noted that in the embodiment, the component elements that areidentical to those of the foregoing first embodiment as described abovewill be simply denoted by the same reference numerals to avoidrepetitions of similar explanations.

Designated at 41 are the inclined covers that are provided respectivelyon the upper surface plate 26C of the left side frame 25 and the uppersurface plate 30C of the right side frame 29. Two inclined covers 41 areprovided to have an interval therebetween in the front-rear direction onthe upper surface plate 26C of the left side frame 25, and the twoinclined covers 41 are provided to have an interval therebetween in thefront-rear direction on the upper surface plate 30C of the right sideframe 29.

Here, the inclined cover 41 comprises three support plates 41A and oneinclined plate 41B. That is, the inclined cover 41 comprises the threesupport plates 41A each of which is formed as a plate body in atriangular shape using a steel plate or the like and is provided to riseon each of the upper surface plate 26C of the left side frame 25 and theupper surface plate 30C of the right side frame 29, and the inclinedplate 41B that is formed as a rectangular flat plate extending in thefront-rear direction using a steel plate or the like, and is inclined inan oblique downward side by being fixed on an upper end of each of thesupport plates 41A.

In the second embodiment, the two inclined covers 41 are arrangedbetween the three upper roller devices 8 on the upper surface plate 26Cof the left side frame 25, and the inclined plate 41B of each inclinedcover 41 is inclined in the oblique downward side from the inner surfaceplate 26A toward the outer surface plate 26B of the left side frame 25.On the other hand, the two inclined covers 41 are arranged between thethree upper roller devices 8 on the upper surface plate 30C of the rightside frame 29, and the inclined plate 41B of each inclined cover 41 isinclined in the oblique downward side from the inner surface plate 30Atoward the outer surface plate 30B of the right side frame 29.

In the hydraulic excavator 1 according to the second embodiment, theinclined covers 41 are provided in each of the upper surface plates 26Cand 30C of the left and right side frames 25 and 29. Accordingly, evenin a case where the earth and sand attached to the crawler belt 10 atthe working of the hydraulic excavator 1 drop down toward the respectiveupper surface plates 26C and 30C of the side frames 25 and 29, it ispossible to drop down the earth and sand along the inclined plate 41B ofthe inclined cover 41. Therefore, it is possible to restrict earth andsand to be accumulated on the respective upper surface plates 26C and30C of the left and right side frames 25 and 29 to restrict interferenceof the earth and sand with the upper roller device 8. As a result, theupper roller device 8 can smoothly operate over a long period of time.In addition, since it is possible to restrict earth and sand to beaccumulated on the respective upper surface plates 26C and 30C of theleft and right side frames 25 and 29, it is not necessary to use a greatdeal of labors and hours for cleaning the accumulated earth and sand toenhance workability of the cleaning work to the hydraulic excavator 1.

It should be noted that in the second embodiment, the inclined cover 41is explained to be formed as a member different from the left and rightside frames 25 and 29, and the inclined cover 41 formed of the differentmember is explained to be fixed on each of the upper surface plate 26Cof the left side frame 25 and the upper surface plate 30C of the rightside frame 29. However, the present invention is not limited thereto,but, for example, the upper surface plate 26C of the left side frame 25may be formed as an inclined surface inclined downward from the innersurface plate 26A to the outer surface plate 26B, and the upper surfaceplate 30C of the right side frame 29 may be formed as an inclinedsurface inclined downward from the inner surface plate 30A to the outersurface plate 30B.

In each of the above embodiments, the respective front flanges 21A and21B provided in the respective front legs 12B and 12C of the centerframe 12, and the mounting plates 34 of the respective front legmounting members 33A and 33B provided in the left and right side frames25 and 29 are respectively fastened by eight bolts 40. On the otherhand, the respective rear flanges 22A and 22B provided in the respectiverear legs 12D and 12E of the center frame 12 and the mounting plates 37of the respective rear leg mounting members 36A and 36B provided in theleft and right side frames 25 and 29 are respectively fastened by eightbolts 40. However, the present invention is not limited thereto, and therespective sections may be fastened by nine or more bolts 40, or byseven or less bolts 40.

Each of the embodiments described above is explained by exemplifying thetruck frame 11 of the lower traveling structure 2 provided in thelarge-sized hydraulic excavator 1 as a truck frame of a lower travelingstructure. However, the present invention is not limited thereto, butmay be applied to a hydraulic excavator of a middle size or small size.Further, the present invention may be applied to a working vehicle alower traveling structure of which is provided with a truck frame, forexample, a hydraulic crane or the like.

DESCRIPTION OF REFERENCE NUMERALS

-   -   1: Hydraulic excavator (Construction machine)    -   2: Lower traveling structure    -   6: Idler wheel    -   7: Drive wheel    -   8: Upper roller device    -   10: Crawler belt    -   11: Truck frame    -   12: Center frame    -   12A: Center frame body    -   12B: Left front leg    -   12C: Right front leg    -   12D: Left rear leg    -   12E: Right rear leg    -   13: Upper plate    -   13A: Upper center plate portion    -   13B, 13C: Upper front leg portion    -   13D, 13E: upper rear leg portion    -   14: Support cylindrical body    -   15: Lower plate    -   15A: Lower center plate portion    -   15B, 15C: Lower front leg portion    -   15D, 15E: Lower rear leg portion    -   17: Front plate    -   18: Rear plate    -   19: Left side plate    -   20: Right side plate    -   21: Front flange    -   21A: Left front flange    -   21B: Right front flange    -   22: Rear flange    -   22A: Left rear flange    -   22B: Right rear flange    -   23: Front bolt through hole    -   23A: Left front bolt through hole    -   23B: Right front bolt through hole    -   24: Rear bolt through hole    -   24A: Left rear bolt through hole    -   24B: Right rear bolt through hole    -   25: Left side frame    -   26, 30: Side frame body    -   26A, 30A: Inner surface plate    -   26B, 30B: Outer surface plate    -   26C, 30C: Upper surface plate    -   26D: Bottom plate    -   29: Right side frame    -   33: Front leg mounting member    -   33A: Left front leg mounting member    -   33B: Right front leg mounting member    -   34, 37: Mounting plate    -   35, 38: Reinforcing plate    -   36: Rear leg mounting member    -   36A: Left rear leg mounting member    -   36B: Right rear leg mounting member    -   39: Female bolt hole    -   40: Bolt    -   41: Inclined cover

The invention claimed is:
 1. A truck frame for a hydraulic excavator andwhich is configured to be divided for transport to a working site,comprising: a center frame of a lower traveling structure on a centralpart of which a support cylindrical body is disposed which rotatablysupports an upper revolving structure, and that includes front legs andrear legs disposed at both sides in left-right directions thereof; andleft and right side frames of said lower traveling structure that arerespectively positioned at left and right sides of said center frame andextending in front-rear directions, and are respectively mounted to endsof said front legs and said rear legs, wherein said center frame furthercomprises: an upper plate on an upper surface side of which said supportcylindrical body is disposed, and at both sides in the left-rightdirections of which upper front leg portions and upper rear leg portionsare disposed; a lower plate that is disposed to face said upper plate inupper-lower directions and at both sides in the left-right directions ofwhich lower front leg portions and lower rear leg portions are disposed;a front plate that closes a front side position between said upper plateand said lower plate; a rear plate that closes a rear side positionbetween said upper plate and said lower plate; and left and right sideplates that respectively close left and right side positions betweensaid upper plate and said lower plate, wherein each of said left andright side frames comprises: an inner surface plate disposed at one ofthe sides of said center frame; an outer surface plate disposed to facesaid inner surface plate and to be spaced therefrom; and an uppersurface plate that connects an upper end of said inner surface plate andan upper end of said outer surface plate, wherein said center framefurther comprises: front flanges protruding in the front-rear directionsfrom said lower front leg portions and rear flanges protruding in thefront-rear directions from said lower rear leg portions; and front boltthrough holes that penetrate said front flanges in the upper-lowerdirections and rear bolt through holes that penetrate said rear flangesin the upper-lower directions, wherein each of said left and right sideframes further comprises: a front leg mounting member having a frontmounting plate that protrudes from said inner surface plate thereoftoward said center frame to be mounted to one of said front flanges anda front reinforcing plate fixed to a lower surface of said frontmounting plate and said inner surface plate thereof to reinforce saidfront mounting plate; a rear leg mounting member having a rear mountingplate that protrudes from said inner surface plate thereof toward saidcenter frame to be mounted to one of said rear flanges and a rearreinforcing plate fixed to a lower surface of said rear mounting plateand said inner surface plate thereof to reinforce said rear mountingplate; and a plurality of female bolt holes provided on said frontmounting plate and said rear mounting plate respectively and disposed inpositions corresponding to said front bolt through holes and said rearbolt through holes, wherein each of said front mounting plate and saidrear mounting plate has a base end side that is respectively welded tosaid inner surface plate of one of said left and right side frames and afront end side that is a flat plate extending horizontally so as toprotrude toward said center frame, wherein each of said frontreinforcing plate and said rear reinforcing plate is a flat platerespectively extending perpendicular to the lower surface of said frontmounting plate and said rear mounting plate, and wherein, in a statewhere said front and rear flanges of said center frame are placedrespectively on said front mounting plate and said rear mounting plateof said front and rear leg mounting members of said left and right sideframes, said front bolt through holes, said rear bolt through holes andsaid female bolt holes are positioned to accept bolts inserted thereinto mount said left and right side frames to said center frame toassemble said lower traveling structure at said working site.
 2. Thetruck frame according to claim 1, wherein said front bolt through holesare disposed at front and rear positions in said front flanges, whereinsaid rear bolt through holes are disposed at front and rear positions insaid respective rear flanges, wherein said female bolt holes aredisposed in front and rear positions of said front leg mounting memberof each of said left and right side frames respectively to oppose saidfront bolt through holes, and wherein said female bolt holes aredisposed in front and rear positions of said rear leg mounting member ofeach of said left and right side frames respectively to oppose said rearbolt through holes.